Astronomers have identified BD+56
2966 as a prime target for the Terrestrial
Planet Finder (TPF),
now planned for launch between
2014 and 2020.

BD+56 2966 designation comes from a catalogue that was originally
published in 1863 by
Friedrich
Wilhelm August Argelander (1799-1875) on the position
and brightness of 324,198 stars between +90° and -2°
declination that were measured over 11 years from Bonn, Germany
with his assistants Eduard Schönfeld (1828-1891) and Aldalbert
Krüger (1832-1896). The catalogue became famous as the
Bonner
Durchmusterung ("Bonn Survey") and is typically
abbreviated as BD. It was later expanded and extended
during the early 20th Century with the
Cordoba
(observed from Argentina) then the
Cape
Photographic Durchmusterung (observed from South Africa).

As a relatively bright star in Earth's night sky, Star A is catalogued
as Harvard Revised (HR) 8832, a numbering system derived from the 1908
Revised Harvard Photometry catalogue of stars visible to many Humans
with the naked eye. The HR system has been preserved through its
successor, the
Yale
Bright Star Catalogue -- updated and expanded through the
hard work of
E. Dorrit
Hoffleit and others. HR 8832 is also listed as HD 219134 in the
Henry
Draper (1837-82) Catalogue with extension (HDE), a
massive photographic stellar spectrum survey carried out by
Annie
Jump Cannon (1863-1941) and
Edward
Charles Pickering (1846-1919) from 1911 to 1915 under
the sponsorship of a memorial fund created by Henry's
wife, Anna Mary Palmer. (More discussion on star names and
catalogue numbers is available from Alan MacRobert at
Sky
and Telescope and from Professor James B. Kaler's
Star
Names.)

The Star

BD+56 2966 is a orange-red main sequence dwarf star of spectral and
luminosity type K3 V. This star has about 81 percent of Sol's mass
(RECONS
estimate), probably between 80 to 81 percent of its diameter
(Pasinetti-Fracassini
et al, 2001), and about 21 percent of its visual luminosity.
According to one secondary reference which has not been verified,
the star may be as enriched as Sol with elements heavier than
hydrogen ("metallicity"), based on its abundance of iron.
It is a New Suspected Variable star with the designation NSV
14458 and a Catalogue of Suspected Variable star as CSV 8833.
Other useful star catalogue designations for BD+56 2966
include: HR 8832*, Gl 892, Hip 114622, HD 219134, SAO 35236,
FK5 875, LHS 71, LTT 16826, and LFT 1767.

Hunt for Substellar Companions

Since BD+56 2966 the star is sort of like a distant cousin
to Sol, some speculate whether it might just be bright enough to
support Earth-type life on a planet lucky enough to orbit in its
water zone. A search for faint companions using radial velocity
analysis found no supporting evidence for Jupiter-sized
sized object within three AUs and objects larger than three
Jupiter-masses within six AUs
(Cummings
et al, 1999). On the other hand, the failure to find large substellar
objects like brown dwarfs or a Jupiter- or Saturn-class planet in a
"torch" orbit (closer than the Mercury to Sun distance) around BD+56 2966
-- with even the highly effective radial-velocity methods of Geoff
Marcy and Paul Butler -- bodes well for the possibility of Earth-type
terrestrial planets around this star.

Indeed, the distance from BD+56 2966 where an Earth-type planet
would be "comfortable" with liquid water is centered around only
0.46 AU -- just beyond Mercury's orbital distance in the Solar
System. At that distance from the star, such a planet would have
an orbital period of about 125 days -- just over a third of an
Earth year. Astronomers are hoping to use NASA's
Terrestrial
Planet Finder (TPF) and the ESA's
Darwin
planned groups of observatories to search for a rocky inner planet in the
so-called
"habitable
zone" (HZ) around BD+56 2966. As currently planned,
the TPF will include two complementary observatory groups:
a visible-light coronagraph to launch around 2014; and a
"formation-flying" infrared interferometer to launch before
2020, while Darwin will launch a flotilla of three
mid-infrared telescopes and a fourth communications hub
beginning in 2015.

Life Around a Flare Star

Many dim, red (M) and some orange-red (K) dwarf stars exhibit
unusually violent flare activity for their size and brightness.
These flare stars are actually common because red dwarfs make
up more than half of all stars in our galaxy. Although flares
do occur on the Sun every so often, the amount of energy released
in a Solar flare is small compared to the total amount of energy
that Sol produces. However, a flare the size of a solar flare
occurring on a orange-red dwarf star (such as BD+56 2966) that
normally has less than 21 percent of than Sol's luminosity would
be more noticeable.

BD+56 2966 is a flare star, like UV
Ceti (Luyten
726-8 B) shown flaring at left. UV Ceti is an extreme
example of a flare star that can boost its brightness by
five times in less than a minute, then fall somewhat slower
back down to normal luminosity within two or three
minutes before flaring suddenly again after several hours.

Flare stars erupt sporadically, with successive flares spaced anywhere
from an hour to a few days apart. A flare only takes a few minutes to
reach peak brightness, and more than one flare can occur at a time.
Moreover, in addition to bursts of light and radio waves, flares on dim
red dwarfs may emit up to 10,000 times as many X-rays as a
comparably-sized Solar flare on our own Sun, and so flares would be
lethal to Earth-type life on planets near the flare star. Hence,
Earth-type life around flare stars may be less likely because their
planets must be located very close to dim orange-red dwarfs to be
warmed sufficiently by star light to have liquid water (about 0.46 AU
for BD+56 2966), which makes flares even more dangerous around
such stars. In any case, the light emitted by late orange-red dwarfs
may be too red in color for Earth-type plant life to perform
photosynthesis efficiently.

Closest Neighbors

The following star systems are located within 10
light-years of BD+56 2966.

With its stars shaped in a "W," this northern constellation was named
by the Ancient Greeks for the mother of Andromeda who claimed to be
more beautiful than the daughters of Nereus, a god of the sea.
Cassiopeia's vanity so angered the sea god Poseidon that he had
Andromeda chained to a rock of the coast as a sacrifice for Cetus
(the monstrous whale) until Perseus rescued her.
For more information on stars and other objects in this Constellation
and a photograph, go to Christine Kronberg's
Cassiopeia.
For an illustration, see David Haworth's
Cassiopeia.

For more information about stars including spectral and luminosity
class codes, go to ChView's webpage on
The Stars of
the Milky Way.